1. Field of the Invention
This invention relates to an improved device for indicating and measuring variations in the resistance of a living body.
2. Prior Art
With the advent of Lafayette R. Hubbard's device for measuring and indicating changes in a living body, the capability of discerning small changes in the resistance of living body through electromechanical measurement was made available. That device includes, generally, a resistance measuring circuit, an amplifier circuit and an indicator circuit. Although adequately suited for its intended purpose of detecting changes in the resistance of a living body, it was not able to accurately indicate the measured changes. Various improvements have attempted to overcome this problem, described and illustrated in U.S. Pat. No. 3,290,589 and U.S. Pat. No. 4,459,995. Such devices operate to generate a signal representative of small measurements in the resistance of a living body. This is then amplified into a signal that is discernable and useful on an indicator perceptible to a human being, such as a visual display. One problem with these devices is that undesirable characteristics in the signal may mask or falsely report small measurements. These undesirable characteristics may be caused by radio-frequency interference and/or internal non-linearities in the device itself. Thus, a need exists for a device that can more accurately indicate changes in the resistance of living body.